Many of today's personal communicating devices employ a silent indication when a call or message is incoming. The indicator is generally a vibration which is transmitted by the appliance in response to the incoming signal. It is necessary that the vibration be sufficiently strong so that it will not go unnoticed. To generate the signal an electrical motor is constructed with a rotating shaft on which is mounted an eccentrically mounted mass. As the shaft rotates, the unbalanced mass generates a vibration that is proportional to the speed and torque of the motor as well as the eccentricity and mass of the rotor. Since these devices are to used in mobile, hand held appliances, power is at a premium in order to allow long periods between charges. In addition weight is a significant factor. Prior attempts to provide an efficient, but strong vibrating signal, involved ironless rotors having windings with brush type commutators. An eccentric mass is mounted on the shaft in addition to the rotor. The use of a brush commutator could generated sparks which would be undesirable in certain conditions and cause communications interference. The use of the external eccentric mass increases the size of the vibrator element and creates difficult mounting problems.
It is a purpose of this invention to design a low profile light weight vibrating motor which generates a strong vibrating signal at low power. The motor of this invention is integrated into the cover of the communicator appliance and can be easily controlled.